溴化锂-水工质对的三相蓄能系统热力学性能分析

Thermodynamic performance analysis on LiBr-H_2O three-phase thermal energy storage system

阐述太阳能空调用溴化锂-水工质对的三相蓄能系统工作过程。为了研究该系统的热力学性能,首先建立热力学模型,然后结合实例使用数学编程软件Matlab进行分析模拟。结果表明:蓄能时,当集热器集热介质(热水)温度从85℃提高至100℃,结晶率可达到81.3%,蓄能密度提高约50%,能量效率仅提高3.8%;当热水流量从0.03 kg/s提高至0.10 kg/s,能量效率几乎不变,结晶率约为30%,蓄能密度提高约15%;当换热器传热性能(传热面积与传热系数乘积)提高125%,结晶率提高约52%左右,蓄能密度提高约30%,能量效率仅提高2.5%;当蓄能速率提高时,能量效率逐渐降低,结晶率和蓄能密度随蓄能速率呈抛物线变化(先逐渐增大后逐渐减小);释能速率满足制冷负荷需求的同时应该尽可能得小。

The working process of one LiBr-H2O three-phase thermal energy storage system used for solar air-conditioning is described. In order to study this system＇s ther- modynamic performance, the thermodynamic model is established first, and then the sim- ulation and analysis Based on one typical case are conducted using Matlab programming software. The results indicate that： in the charging process, when the temperature of hot water rises from 85℃ to 100℃ ,the crystallization rate can reach 81.3% ,the energy stor- age density can increase by about 50%, and the energy efficiency can only increase by 3.8%. When the hot water flow rate increases from 0.03 kg/s to 0.10 kg/s, the energy efficiency hardly changes, the crystallization rate is about 30%, and the energy storage density increases by about 15%. When the heat transfer performance of heat exchanger （the product of heat transfer area and heat transfer coefficient） increases by 125%, the crystallization rate can increase by about 52%, the energy storage density can increase by about 30 %, and the energy efficiency can only increases by 2.5 %. When the solution flow in the charging phase increases, the energy efficiency gradually reduces, the crystallization rate and energy storage density change by parabolic curves with the solution flow, which increase gradually first and then decrease gradually. The solution flow in the discharging phase should be as small as possible, but on condition that it＇s sufficient to meet the required cooling load.